Grade needs to raise cash as the group faces an advertising slump and has to service its debt and pension fund.
ITV owns the SDN digital television business, which operates the Freeview multiplex that hosts Channel Five's channels, as well as the shopping channel QVC. The sale is expected to raise around £200m.
SDN is profitable, with revenues of £36m in 2007, but is not seen as central to ITV's core activities. The most likely buyer is Arqiva, which already owns the other two commercial multiplexes on Freeview.
Grade will present his rescue plan for ITV to the City when he announces the group's annual results on March 4th.